The information in this document is based on these software and hardware versions:

Cisco Unified CM 6.x and later.

Cisco ATA 186/187 version 3.2 (4).

The information in this document was created from the devices in a specific lab environment. All of the devices used in this document started with a cleared (default) configuration. If your network is live, make sure that you understand the potential impact of any command.

The issue is you cannot add a second line on Cisco Unified CM to ATA 187.

ATA 187 auto-registers to Cisco Unified CM with two MAC addresses. One is the MAC address from its back cover, the other one is shifted MAC (for example, MAC is AABBCCDDEEFF, and shifted MAC is BBCCDDEEFF01 ). In order to resolve this issue, you need to use the shifted MAC to provide the second port of a DN.